1906.] 0)1 The Steam Tarhine on Land and at Sea, 83:-) 



displacement, and 21,000 horse-power, is a sister vessel to the 

 " Caronia," propelled by quadruple expansion engines of the most 

 economical tvpe, and during the last four months the consumption 

 of coal in the two vessels has been carefully measured, but it is too 

 soon as yet to give the results. However, on the official trials, the 

 turbine vessel exceeded the speed of her sister ship by one knot. 



Some of the advantages found to exist with turbine propulsion 

 are, that the propellers never race in the heaviest seas, and that, as a 

 consequence, the speed is better maintained under all weather con- 

 ditions ; and the cause of this is to be traced to the smaller diameter 

 of the propellers, wider blades, and deeper immersion. There is also 

 much less vibration. 



The tendency of late has been to increase the reversing or astern 

 power of turbine vessels to such an extent that, in many cases, the 

 stopping and manoeuvring powers have been equal to those of twin 

 screw vessels with reciprocating engines. The starting of turbine 

 vessels is relatively quick, for the torsional force of a turbine, when 

 starting from rest vdih. full steam on, is at least 50 per cent, greater 

 than the torque at the usual running speed, because the blades, when 

 running slowly, meet the full blast of the steam instead of moving 

 with it as they do at their usual speeds. AVith ordinary engines, 

 the starting torque does not exceed the torque at full speecl. tVhen 

 manoeuvring, turbines cannot fail to respond when steam is turned 

 on, for they have no dead centres upon which to stick, as in the 

 reciprocating engine. 



From the fact that the faster and larger the vessel the better has 

 been the performance, it seems safe to infer that the two very large 

 and fast Cunarders now building will give satisfactory results, and 

 the same may be expected as regards new turbine construction in 

 ships of war. 



The diagram. Fig. 7, shows the various steps in the development 

 of the steam turbine as applied to marine propulsion. 



The total horse-power in steam-ships sailing under all flags is at 

 present about eight millions. Of this total, about one quarter, or two 

 millions, is in the faster class of ships to which turbines are suitable. 



Of the remaining six millions horse-power, about three to four are 

 in the larger class of ocean tramp, and the remainder in coasting 

 steamers and small river boats, etc. 



By a combination of the turbine with the reciprocating engine 

 there seems to be no doubt that the three or four millions horse- 

 power of large ocean tramps may be successfully propelled with a saving 

 of from 15 to 20 per cent, in cost of fuel. 



This combination has not yet been applied to any vessel. In it 

 the reciprocating engine first expands the steam from the boiler down 

 to about atmospheric pressure, and then passes on to the turbines, 

 which complete the expansion down to the condenser pressure. The 

 turbine thus utilises the lower part of the expansion, which the 



